Plant roots

Assignment 1:

Go to the garden or the school playing fields and collect one small example of each of four kinds of common plants. Choose weeds, if possible. Ensure that you remove the plant with its root system intact. Rinse off any soil and arrange the plants on a sheet of clean paper.

Do you observe any noticeable differences with regard to the root system?

If you are lucky your plant samples will have two different kinds of root system. Sketch the two main types of root system. Your educator will provide the necessary guidance.

The TWO types of root system are known as the ADVENTITIOUS ROOT SYSTEM and the TAP ROOT SYSTEM.

Plants that have a taproot system have a main root that grows deep into the soil. Most of the plants that survive for more than a year (perennials) have a taproot system. This type of root system can reach water that is far below the soil surface and can anchor the plant. High trees and shrubs and bushes need such root systems. They belong to the group DICOTYLEDONS. They develop from seeds that have two seed leaves or cotyledons, like the seed of the bean plant. Many dicotyledonous plants, of course, are also annuals, but they do have taproot systems.

Monocotyledons, e.g. grasses and maize plants, are annuals. As they grow for one season only, they do not need very deep root systems. They actually need a wide, shallow root system to absorb all the moisture that might reach the soil. MONOCOTYLEDONOUS plants have adventitious root systems and develop from seeds that have one cotyledon, e.g. a maize kernel.

A taproot system consists of one main root, the taproot, and lateral roots that grow from it.

An adventitious root system consists of equally sized roots that grow from the base of the stem and are called adventitious roots. These roots are not branched.

Assignment 2:

Provide the correct labels for the sketches of the two types of root systems.

1. Which type of root system would you find with petunias, which are annuals?

2. Why do petunias develop this type of root system?

3. Which type of root system would an oak tree have?

4. Why would a tree need this type of root system?

5. Do trees have adventitious roots? Provide an explanation for this.

6. Can lateral roots develop from adventitious roots? Explain your answer.

7. Explain the main functions of roots.

Assessment of Root systems

Were you able to distinguish different types of roots and apply your knowledge?

[LO 1.2, 2.4]

Take a fresh plant with roots, rinse the roots to remove the soil and carefully examine the roots. Are you able to see the fine, hair-like growths at the tips of the roots? They will be particularly visible on bean plants that you germinate from seeds yourself. These structures are known as root hairs, or radical hairs.

What is the function of a root hair?

The following is an illustration of the tip of a root:

Figure 1

Assignment 3:

Explain what happens in each of the following regions:

Root hair region:

owing region:

Root tip:

Root hairs consist of special cells on the outer surface of the root right behind the growing region, which increase the surface of the root so that the maximum amount of water and mineral salts can be taken up from the soil.

Assignment 4:

Make a drawing showing the structure of a typical root hair. Provide your drawing with labels and a caption.

The root hair penetrates the small spaces between the particles of soil to suck up the moisture that is trapped between the soil particles. Then it is the function of the next plant organ, namely the plant stem, to conduct the moisture further.

Assessment: Root hairs

Were you able to draw the basic sketch?

[LO 1.2]

Activity 2

Assignment 1

ROOT SYSTEMS

Assignment 2

A taproot system consists of one main root, the taproot, and lateral roots that grow from it.

An adventitious root system consists of equally sized roots that grow from the base of the stem, the adventitious roots.

The life cycle of annuals is completed in a year – they do not need taproots – and they will therefore have an adventitious root system

Trees have a taproot system because they require to be anchored deeply and have to obtain water from deep below the ground.

As adventitious roots grow from stems, they will be of no value for trees that need deep anchoring.

Lateral roots only grow out of other roots.

Main functions of roots:

anchoring

uptake of water

uptake of mineral salts in solution

conducting water to the upper parts of the plant

When a root system is investigated, the following structure can be observed:

Figure 2

Assignment 3

Root hair region: region where root hairs develop

Cell lengthening region: region where cells lengthen and differentiate

Cell division region: where cells divide

Meristem: general region where cell division and cell lengthening occur

Root tip: Protects the sensitive foremost growth tip by keeping it slimy to prevent wear.

The srtucture of the root hair is of importance in further studies in Biology.

Assignment 4

This is what we shall focus on next.

Root hair

Figure 3